Numbers 22:20

And God came unto Balaam at night and said unto him, If the men come to call thee, rise up and go with them; but yet the word which I shall say unto thee, that shalt thou do. This was not a concession due to a change of mind, for God expressly stipulates that only that saying dared to be pronounced over Israel which He would give to Balaam. It was God's way of dealing with Balaam's defiant mood. Jehovah's purpose may have been, as one commentator has it, to reveal Himself in such a mighty manner before the eyes of Balaam as to cause him to turn to the true God in real change of heart. But one fact is clear, namely, that through the disobedience of Balaam the Lord brought a blessing upon His people and caused one of the most beautiful Messianic prophecies of the Old Testament to be spoken.